Manuel II Paleologus reigned as emperor of Byzantium from 1391, the year in which he is believed to have composed the text from which the Pope quoted last week, until his death in 1425. A brief overview of his experience of Islam:
1390: Manuel is sent as a hostage to the court of Sultan Bayezid I. As his writings demonstrate, he reads widely in Muslim texts and engages in repeated debates with Muslim scholars. He is also forced to participate in an attack on his own people, the siege of Philadelphia, which eliminated the last Byzantine settlement in Anatolia.
1394-1402: The Ottomans besiege Constantinople. For some five years, Manuel directs the defense of the city in person. Then he entrusts Constantinople to his nephew and embarks on a tour of the West, seeking assistance.
1422: The Ottomans attack Manuel in Constantinople once again.
By the time of his death in 1425, Manuel had spent virtually his entire adult life in the struggle against an armed and expansionist Islam—and in 1453, just over a quarter of a century later, the Ottomans would finally conquer the empire he had defended.
The point? One may certainly argue that Islam had no monopoly on fourteenth and fifteenth century violence—Manuel himself had to resist several attempts by members of his own family to deny him the throne. What one may not, argue, I think, is that Manuel lacked the authority or knowledge to speak about Islam. When he described efforts “to spread by the sword the faith [the Prophet] preached,” he wasn’t mouthing some sort of ignorant medieval prejudice. He knew exactly what he was talking about.